Re: [boost] [any] boost::get style accessors

Subject: Re: [boost] [any] boost::get style accessors
From: Stefan (mstefanro_at_[hidden])
Date: 2010-04-29 12:50:38

vicente.botet wrote:
> ----- Original Message ----- 
> From: "Christoph Heindl" <christoph.heindl_at_[hidden]>
> To: <boost_at_[hidden]>
> Sent: Thursday, April 29, 2010 5:50 PM
> Subject: Re: [boost] [any] boost::get style accessors
> 
> 
> 
> On Thu, Apr 29, 2010 at 1:10 PM, Stewart, Robert <Robert.Stewart_at_[hidden]> wrote:
>> Christoph Heindl wrote:
>>> On Wed, Apr 28, 2010 at 8:00 PM, Stewart, Robert
>>> <Robert.Stewart_at_[hidden]> wrote:
>>>
>>>> At that point, I think they should be on par with any_cast
>>>> rather than built on any_cast so that exceptions needn't be
>>>> translated. Exception handling overhead is too costly to do
>>>> it twice when it isn't necessary.
>>> I agree. I don't see any added value by using bad_get, except all
>>> boost:get accessors would throw bad_get exceptions.
>> Perhaps you missed my point. I was suggesting that your gets be implemented at the same level of access as any_cast so no exception translation were needed. In other words, take code straight from any_cast and use it to implement get, provided bad_cast is deemed useful.
> 
> Indeed I did. In boost 1.42 this corresponds to duplicating ~40 lines
> of code to exchange the type of exception thrown. I'm not too keen of
> doing this (not talking about the tests I would have to duplicate too)
> :) Of course, code could be refactored to refer to a common set of
> methods that take the exception to throw as templated argument, if
> desired.
> 
> _______________________________________________
> +1 for refactoring.
> Best,
> Vicente
> 
> 
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> 
It would make little sense to have a boost::get working with both 
Boost.Variant and Boost.Any transparently if it does not have a 
consistent behavior (i.e. the same way of signaling a problem). I don't 
think refactoring some code to make the behavior consistent will be 
problematic.
Currently, boost::bad_get is deriving directly from std::exception 
whereas boost::bad_any_cast is deriving from std::bad_cast. It might 
make more sense to have both boost::bad_get and boost::bad_any_cast 
derive from a common exception class type, such as boost::bad_cast (or 
maybe have boost::bad_get derive from std::bad_cast)

Yours,
   Stefan